Field of the Invention
The present invention relates to an organic polymeric porous body used for insulating materials, lightweight structural materials, and absorption materials, acoustic absorbing materials, and catalyst carriers, substrates for electronic components having a low dielectric constant, and materials for aeronautics and astronautics and for transportation vehicles having heat insulation properties, acoustic absorption properties, and lightweight properties. The present invention also relates to a function member used for an image forming apparatus such as copying machines, printers, and facsimiles, and to an image fixing apparatus using the function member.
Description of the Related Art
An organic polymeric porous body is produced in a combination of various polymeric raw materials and a porosification technique, and manifests characteristic function thereof according to a porosity size, a porosity ratio, and surface properties. For example, foamed bodies such as foamed polystyrene and foamed polyurethane are used in broad fields such as houses, automobiles, and household appliances as lightweight structural materials, insulating materials, and shock absorbing materials. Porous films having a finer porosity size from nanometers to micrometers are also used as separation membranes, permeable membranes, separators for secondary cells, and hemodialysis membranes. Fields where the technique is used are increasing every year.
Recently, porous films are also developed particularly with respect to the so-called engineering plastics (hereinafter, engineering plastics), i.e., polymeric materials having thermal resistance against a temperature exceeding 200° C. Making use of properties such as high mechanical properties and chemical resistance, examples in which the engineering plastics are used also under environments with large chemical and physical load such as those of aerospace industry and transportation vehicles are increasing. A porous film using the engineering plastic resin can be used by making the porosity ratio high to some extent to enhance heat insulation properties. For this reason, development of various applications such as heat-resistant filters of high durability, low-k films for electronic component substrates, and insulating materials for aeronautic and astronautic rockets are considered.
Also in printing fields such as electrophotography and printers, there are many environments having exposure to a large amount of a solvent under high temperature and high pressure, for example, transfer or fixed portions of a toner and discharged portions of a dye in image forming apparatuses. In order to give advanced features to a material that forms these portions (for example, an intermediate transfer belt, an organic photoreceptor, a roller, and an ink head) to realize a new printing system, the necessary condition is use of a material that can bear the above-mentioned environments. Even in the present situation, polyimides are usually used for an intermediate transfer belt in an electrophotographic apparatus.
Porosification of a resin is a very effective method upon giving advanced features to the material as mentioned above. On the other hand, for the above reason, use of an engineering plastic porous film is very effective upon applying a porosified material to the printing field to develop a new printing method with energy saving, a high speed, and high image quality. In the present situation, examination is conducted as shown in Patent Documents.
Various methods such as an electrophotographic method, an electrostatic recording method, an inkjet method, and a thermal recording method are used as a printing method for the image forming apparatus at present. Of these methods, the electrophotographic method is a method widely spread mainly in offices for advantages such that operation of the apparatus is easy, a large amount of recorded images can be printed in a short time, and recorded matters have small deterioration over time and high preservability.
The electrophotographic image forming apparatus includes a charging apparatus that charges a photoreceptor, an exposing apparatus that irradiates the charged photosensitive body surface with a laser beam to form an electrostatic latent image, a developing apparatus that forms a toner image from the electrostatic latent image on the surface of the photoreceptor, a transfer apparatus that transfers the toner image on the surface of the photoreceptor onto a recording medium, a fixing apparatus that fixes the toner image transferred on the recording medium to the recording medium, and a cleaning apparatus that removes a toner that remains on the surface of the photoreceptor after transfer of the toner image, for example.
Examples of a main method for fixing the toner image on the recording medium include a method in which a heat fixing roller and a pressurizing roller parallel to and in pressure contact with this heat fixing roller are provided, and a recording medium having a toner image attached thereto is passed between the pressurizing roller and the heat fixing roller; thereby, the toner is softened with heat of the heat fixing roller, and the toner image is fixed on the recording medium by applying pressure between the pressurizing roller and the heat fixing roller.
In such a heat fixing apparatus, a heat fixing roller having a releasing layer made of a fluororesin for prevention of toner adhesion provided on an outer circumferential surface of a core bar composed of a hollow cylindrical body made of aluminum is used, for example. A halogen lamp or a heat source of an induction electromagnetic heating method is disposed in a hollow portion of the core bar of the heat fixing roller, and the heat fixing roller is heated from the inside thereof by the radiant heat or induction heating.
For the electrophotographic image fixing apparatus, a belt nip method including a heating roller having a heating source, a belt that contacts the heating roller by pressure and rotates with the heating roller, and a fixing roller arranged within this belt is known. Moreover, a method in which a belt is contacted by pressure with a heating roller by a pressure pad (hereinafter, referred to as a “heat roller fixing method”) is also known.
The heat roller fixing method is suitable for higher-speed printing and mass printing because the entire heating roller can be kept at a predetermined temperature. However, the heat roller fixing method has problems such that rise time of the heating roller reaching the predetermined temperature is longer, and power consumption is larger. Particularly, approximately 80% of heat transfer from the heating roller dissipates to the recording medium or the outside of the system. For this reason, a problem of significant increase in power consumption arises in high-speed printing.
Then, methods for providing a porous layer in a belt material have been proposed. Japanese Patent Application Laid-Open No. 2006-133704 has proposed suppression of increase in a surface temperature of a photoreceptor by providing a porous layer in a belt material that serves both as an intermediate transfer body and a fixing body. Moreover, Japanese Patent Application Laid-Open No. 2008-52201 has proposed a belt material having a porous layer as a belt material with high elasticity and high heat resistance. Porous polyimide described in Japanese Patent Application Laid-Open No. 2003-138057 and a porous engineering plastic material having independent porosities described in Japanese Patent Application Laid-Open No. 2009-073124 are proposed as a method for producing a porous layer having fine porosities.